Author Topic: Butterfly knot - various loading profiles  (Read 480 times)

agent_smith

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Butterfly knot - various loading profiles
« on: May 11, 2020, 07:20:35 AM »
#1053 Butterfly knot has been a workhorse in the rope access, climbing and vertical rescue communities.

I am currently writing a new technical paper on this knot.

There is some discussion in another thread that is drifting into the realm of academia and knot topology  - and this new topic thread may be more in tune with that particular discussion.

A precise definition of various loading profiles on knots has not been peer reviewed and published in a technical paper (as far as I am aware).
For instance, the notional concept of 'ring loading' may be diluted to encompass specific loading profiles on the eye of a Butterfly knot.
I am of the view that the term 'ring loading' may be too general - and not define (with precision) the direction of loading on various rope segments linked to the knot core.

Circumferential loading (ie cylinder/hoop stress) is expanding the eye in all directions - rather than a single defined axis.

The eye of a Butterfly can be loaded in several different ways - all inducing various effects on the knot core.

The term 'Offset loading" is also being applied and interpreted in differing ways.

I will be investigating all of these definitions and resulting effects in my new paper...
I have already corresponded with some colleagues - who have collaborated and contributed in the past.

Topology is a complex subject dealing with a mathematical knot (which has no ends).
While indeed very interesting, practical knots do have ends... with various loading profiles and jamming thresholds - which are not accounted for in topology.

KC

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Re: Butterfly knot - various loading profiles
« Reply #1 on: May 11, 2020, 09:50:26 AM »
Very nice!
i think the eye is best loaded less than the SParts;
and if eye not unlooaded /used to isolate damage or just as stopper
>>that any pull on eye is best perpendicular to the competing SParts.
Thus the opposing pulls of the SParts forms the major axis
>>and eye the lesser, and if any pull 90 degrees is most balanced
>>and geometry flows smoothly to that.
« Last Edit: May 11, 2020, 10:57:49 PM by KC »
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agent_smith

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Re: Butterfly knot - various loading profiles
« Reply #2 on: May 12, 2020, 02:46:55 AM »
per KC:
Quote
i think the eye is best loaded less than the SParts;
and if eye not unloaded /used to isolate damage or just as stopper
>>that any pull on eye is best perpendicular to the competing SParts.
Thus the opposing pulls of the SParts forms the major axis
>>and eye the lesser, and if any pull 90 degrees is most balanced
>>and geometry flows smoothly to that.

Thanks... I am going to run some eye loading tests of #1053 Butterfly in human rated EN 1891 rope.
I will experiment with various dressings of the eye (eg twisting the eye).
I'll also through load (SPart-to-SPart) with the eye isolated - and see if it remains jam resistant right up to MBS yield point.

Am also going to include various modifications and alternative TIB bi-axially loaded knot.
Will also investigate the 'Mobius' dressing of the derived Butterfly eye knot that is Either End Loadable (EEL).... including all of the derived eye knots from the Butterfly bend.
There will be numerous high quality images of #1053 Butterfly and its derived Butterfly bend along with some history (eg AA Burger; Wright & Magowan; and Phil D Smith).

If you are interested to be a contributor and be cited in the paper, PM me.

agent_smith

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Re: Butterfly knot - various loading profiles
« Reply #3 on: May 12, 2020, 03:16:56 AM »
Xarax has pointed me to the following:
Link: https://igkt.net/sm/index.php?topic=3827.msg22680#msg22680
Derived from #1408?
Is this an original creation?
I have not investigated jam resistance in various loading profiles... is there test data in existence?

And a discussion on symmetry:
Link: https://igkt.net/sm/index.php?topic=4425.msg27940#msg27940

All possible candidates for inclusion in new paper on the Butterfly (bi-axially loadable TIB eye knot).

Dan_Lehman

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Re: Butterfly knot - various loading profiles
« Reply #4 on: May 12, 2020, 09:52:15 PM »
Xarax has pointed me to the following:
Link: https://igkt.net/sm/index.php?topic=3827.msg22680#msg22680
Derived from #1408?
Is this an original creation?
Yes, so far as I'm aware.  (I.e., while I know that
*I* tied it while fiddling --though I think with actual
goal in mind, this time!  :D --, I can't say for sure
that someonElse hasn't done similarly.)

Beyond that then came the symmetric, "twin-eye"
versions.  I did like above with the zeppelin
--i.e., had first asymmetric than symmetric finds--,
and shakehands, and #1452 (and the same-rotation
butterfly, with one fig.8 half, the extra twist
getting the rotational agreement with the remaining
overhand half).

And then gazillions of other *directional* eye knots,
though I realize that that qualification comes with
some challenge : who's to say that loading it in the
*other* direction is verboten?!  In CMC Rope Rescue
testing, they found the offset fig.8 eye knot stronger
than the inline one, through loaded !

--dl*
====

tsik_lestat

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Re: Butterfly knot - various loading profiles
« Reply #5 on: May 24, 2020, 09:44:37 PM »
How about a bowline knot, based on ABK's TIB nipping structure?

Perhaps, it may not be directly related to the midline concept, but it seems to me like a secure and compact way to load the eye of this pretzel/butterfly based nipping structure, when stabilized with a conventional U braced bight for a bowline construction.

Xarax has submitted a knot like this, long before, at his pretzel/Eskimo thread, so i have attached a pointer to his work.

Link : https://igkt.net/sm/index.php?topic=4464.msg33112#msg33112

Under closer inspection to its core nip, one can acknowledge the butterfly pattern.

Is it proper to attach a moniker like butterfly bowline? (my term) :)

PS : Insert the WE down through the center of the two loops, and you will form Alpineer's tresse!
« Last Edit: May 24, 2020, 10:00:39 PM by tsik_lestat »
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